Posted
by
CmdrTaco
on Tuesday September 14, 2010 @10:04AM
from the can-you-hear-me-now dept.

sweetpea23 writes "Grown-up versions of femtocells — devices which beef up 3G network strength in the home — are set to take over parts of the outdoor cellular networks, according to technology vendor picoChip. Femtocells — such as Vodafone UK's Sure Signal device — are cut-down versions of mobile phone base stations, redesigned to operate inside buildings, using home broadband networks to route 3G data onto the Internet. Now, picoChip, which claims to provide 70 percent of the chips used to make femtocells, has unveiled a toughened up version, which takes the femtocell idea back out onto the streets."

Not really weird. It's probably a legal requirement to have a GPS location of every cell on the network. AGPS, cell phone tracking and all that. The police wouldn't be happy with you being able to make cell calls from any network connection without being traceable, and AT&T probably wants to prevent overseas use as well.

This makes sure you aren't full of shit when you put in the device's physical mailing address. When you call 911, att wants to make sure the paramedics go to the right place. If the address doesn't match the GPS cords, then the microcell doesn't work.

These things are a bit rubbish. At least tonight it is. I bought one today. I can see that it establishes a VPN connection with nat tunneling. But stlll the fourth light doesn't come up, which means it's ready for use (Vodafone sure signal, UK). I did see it flash the fourth light, implying it is updating the software, then it went through a phase akin to a reboot. But not it mostly exchanges lots of ESP encapsulated packets and tons of NTP transfers and no availability. I'll see what it does in a day, but

Actually, after leaving it communicating furiously for about 8 hours it became ready. God knows why it does that but telling customers that it will take that long could remove a lot of time wasted. Also it sends a furious spurt of ntp traffic about evey minute. Seems a little over the top.

It does work though so far.It just uses nat traversal ipsec so most routers would need no modification I think.

typically you buy them from your operator. so instead of beefing up the network, they could sell you a femtocell. nice, eh?

basically this article is just about a femtocell parts provider getting a foot in the door for providing parts for basestations, which isn't that shocking, considering they're already doing basestations, but calling them femtocells.

“Instant messaging and Exchange are the worst offenders,” claiming that a smartphone with “always on” applications like Exchange - while doing very little - can produce the same signalling load on the network as a device making 1000 voice calls per day.

I'm not trying to be facetious, but how does a phone with Exchange produce the same amount of load on a network as a device that's constantly making voice calls? I realize that the phone will be signaling to a server to keep data synced, but how does it produce that much load?

“Instant messaging and Exchange are the worst offenders,” claiming that a smartphone with “always on” applications like Exchange - while doing very little - can produce the same signalling load on the network as a device making 1000 voice calls per day.

I'm not trying to be facetious, but how does a phone with Exchange produce the same amount of load on a network as a device that's constantly making voice calls? I realize that the phone will be signaling to a server to keep data synced, but how does it produce that much load?

Well... Exchange is a server product... So I'd assume it's handling a fairly large volume of traffic...

Sarcasm aside, I assume they mean it's running a mail/PIM client talking to an Exchange server. Which will be chatty. There's constant updates and checking for updates and whatnot. But I honestly can't imagine the traffic is really that high volume. We're talking about, essentially, text messages. Maybe some HTML formatting... An attachment or two here and there...

ActiveSync is HTTPS traffic. However, Exchange is "chatty" because both iPhone and Android implementations don't handle "IDLE" part of it really well. Sense Mail client ignores ActiveSync notifications that individual email has changed and issue the command to list all mails in folder again. iPhones do similar shenanigans. On average, according to my Active Sync logs, iPhone 3GS on iOS 3.x connects 4x then Winmo 6.5 phone.

Also, since a data connection is still open, I imagine that means a channel is locked

It could be because the phone calls are 13 kbps, and perhaps once connected use a static path through the network for all data.

If "Signaling Load" means non-data data (if I knew more I could probably give it a level), it could be routing each packet with as much signaling as an entire phone call, though that would quickly get beyond 1000 calls/day.

Also, is this over a 3G/3.5G with separate data and voice, or true 4G where everything gets packetized and pushed over IP? I might be able to see someone with Exchange who gets a lot of Excel spreadsheets pushed to their device having more network traffic than a voice call, but a push or IMAP IDLE notification doesn't take that much bandwidth by itself.

I'm not trying to be facetious, but how does a phone with Exchange produce the same amount of load on a network as a device that's constantly making voice calls? I realize that the phone will be signaling to a server to keep data synced, but how does it produce that much load?

Because signaling traffic and user traffic are handled differently.

A very rough analogy to TCP/IP:
Signaling traffic is similar to SYN, ACK, DNS, DHCP, STP, ARP, SMB and all the other stuff you see on a normal LAN that isn't user payload. On a GSM/UMTS network, this stuff is running on a separate virtual channel from the user traffic (voice or data). Think of it like a separate VLAN which has a max bandwidth allocated to it. (by design)
Basically, the "overhead" packets clog the signaling channel, even though the traffic channel still has oodles of bandwidth available. SYN flood anyone?

I'm not trying to be facetious, but how does a phone with Exchange produce the same amount of load on a network as a device that's constantly making voice calls? I realize that the phone will be signaling to a server to keep data synced, but how does it produce that much load?

Quite easily, actually. It's also the reason why the iPhone is so horrible on the AT&T network.

Basically, when your phone is "attached" to the cell network, it's communicating with the base station on a control channel. Similar to ISDN control channels, it's use for call setup/termination, management and other things. To optimize for power, the mobile station "pings" the base station with presence information (basically saying "i'm here"). This keeps the power-hungry transmitter off and only turns it on for the briefest of times. The receiver is also kept off, but it consumes less power so it can be turned on more frequently to listen for network messages, perform signal analysis (is it getting weak? Does the phone need to find another tower?). This is why if you're in a marginal signal area, your phone will consume more power - the transmitter will have ot use higher power to talk to the tower, and worst case is if you're in a marginal area between cells where the phone has to be constantly doing the handoff between cells (consuming lots more transmitter time).

Now, back to the topic at hand. Making a data "call" is exactly the same way - the phone uses the control channel to set up the call (find an uplink and downlink frequency) as well as any other network parameters, like maybe where in the frame it can transmit and receive its data on. Of course, this keeps the receiver on and the transmitter has to be active, so it consumes more power than idle. So when you want to maximize endurance, you want to tear down the data connection ASAP, which requires another control message. Depending on the application, this can mean setting up and tearing down hundreds of times, which consumes valuable control channel bandwidth.

So now your phone is making hundreds of "calls" continually as it sets up and tears down the data connection, which consumes the control channel bandwidth leaving less for SMS, other call setup/teardowns, handoffs, and the like.

Most North American carriers have the problem because the control channel bandwidth is fixed. Most rest-of-world carriers don't because texting is hugely popular, and SMS ends up consuming a rather significant chunk of control channel bandwidth. So those carriers long ago upgraded to dynamic control channel sizing to ensure that there's enough spare bandwidth for calls, voice or data. Texting is only really taken off in North America the past few years, and the iPhone was really also the first phone that was extremely aggressive on power savings by practically tearing down the data connection during pauses. End result, control channel overload leading to dropped calls (hard to be handed off the target cell can't handle the handoff request), missed calls, delayed text messages, and slow data.

I'm guessing Exchange may use a protocol that allows for frequent bringups and teardowns, especially amongst the more aggressively power saving phones.

This is a problem with all the carriers, especially since iPhones and Android phones are popular. If the Verizon iPhone is as popular as everyone makes it out to be, VZ could be in for a world of hurt if they don't already have the ability to dynamically adjust control channel bandwidth. It's also why early AT&T phone bills were more like phone books - because every time the data "call" is made, it's logged for billing purposes. This could result in pages of log entries just over the course of a browsing session as the data connection is brought up and down each time.

Short answer: 3G sucks for internet access. tlhIngan below has a more detailed explanation what happens when a phone dares to use data service.

Longer answer: Mobile telcos love to control the data flow. And when they designed data for 3G, they had more a "walled garden" concept in mind (which would have all services inside the operator network.) As they tried to include "internet" in their 3G design, they tried to keep all the control they have on their voice network. The result was a mind-boggingly complex

simple things like "permanent TCP connection to whereever" One of the things that anyone who designs a protocol that uses long running TCP connections will learn either from others or from experiance is that TCP handles the case of a long running connection with little to no data flow rather badly especially once nats get involved. Connections that have been up for a long time sometimes drop out and worse the endpoints don't always notice they have dropped out for some time.

Each time there's a voice call there's a signaling load when setting up the call. There's a little bit when moving between cells, and a little to terminate a call.

Each time a phone establishes it's tcp/ip connection similar things occure, because the phone is NOT always connected to the network. Its as-needed. Exchange/pop3/imap are all set up to check email on an interval. Each phone is different, but lets say you're phone is doing SOMETHING every minute (exchange in active sync mode can go down to a 6

I think the key word is "signalling load". Raw data capacity isn't the only thing that is in limited supply on most networks. Especially networks like GSM that keep the control and data channels seperate.

I could well imagine that keeping a GRPS connection up 24/7 would put far more load on the signaling systems than making circuit switched voice connections every so often.

For an analogy/.ers are likely to be familiar. Send large packets over ethernet with even with consumer grade hardware you can max out f

This is neither new nor going to happen any time soon. The cellular industry is talking about femtocells for a few years already, as this is more or less the only practical way of getting good coverage with high (think LTE) throughput. The problems with femtocells are numerous and even though vendors such as picoChip would love to see femto deployments today, providers will not rush into it until they figure out how to solve these problems. Today's cellular network work that good partially thanks to careful

nobody can prevent me from taking my femto Node B to a different country where it would work on a spectrum allocated to somebody else.Wouldn't GPS be a trivial soloution to that problem? Just make the cell refuse to come up if it's too far from it's authorised location.

Home Node B devices are not repeaters. They will actually increase the available bandwidth for large number of users as they will be able to transmit with higher modulation on shorter distance, i.e. they will be more spectrum efficient.

Aren't these home signal booster things just repeaters? If so, what happens to mobile bandwidth when a lot of these repeaters are used instead of actual basestations?

I think an interesting followup question to that is whether all of these femtocells will increase mobile bandwidth but will decrease the bandwidth available from your internet connection overall. The ISPs are complaining already about streaming video and power-users downloading too much. Imagine if the ISPs also had to absorb a chunk of cell phone traffic as well.

I don't know about AT&T, but Verizon does bill you normally, even if you're using a femtocell.

With the AT&T device, they have an unlimited minutes option (that probably costs extra, but nevertheless is available), where all calls that originate on the femtocell are not charged towards your plan. Roaming to and from the femtocell works exactly the same as to normal cell towers. That means you can start a call at home, talk for hours while driving around, etc. and still not be charged for it.

As you implied, they are really just VoIP for your cell. That said, have you (or anyone else on/. for that matter) used one? How do they perform voice connection/quality-wise to traditional consumer level VoIP (read: Skype, Vonage, Google calling, etc.)?

I haven't used one but I'd expect call stability to be much the same as any other VOIP. That is totally dependent on the network conditions between you and your call provider. If the network is mostly loaded with protocols that play nice and isn't loaded too heavilly voip works great. If the network is heavilly loaded with agressive protocols like bittorrent it will probablly be shit. Jitter is the enemy of things like VOIP.

As for voice quality i'd expect that to be much the same as any other cellphone. I d

Interesting. I hear you on the jitter. Had Vonage for a while and it was jitter 70% of the time. And that was with a dedicated hardware router. One would naturally assume the quality would be better. Funny part is that a simple software program with no dedicated hardware or optimizations--Skype--performed almost flawlessly. And I don't have conflicting protocols like Bittorrent running.

I heavily looked into VoIP. I couldn't justify the phone company saying they would charge me $40/mo for unlimited, and with

So let me get this straight. I already pay at&t over 100$ a month, but I can't use my cell phone in my new apartment because I have a crappy signal (other providers are fine, but I'm locked into my contract for another year), so I can PAY them for a device to make calls over MY internet connection so they don't have to upgrade their shoddy network! bah humbug!

Note I do have at&t and have no issues at home, but this is the situation a friend of mine is going through and they want him to buy this device to use a service he's already paying for.

On top of that they charge to 20 bucks a month for unlimited minutes to use the service or you end up using your minutes on your plan. So you get changed for the device, and charged to use the device. All so AT&T doesn't have to fix their network. Who says the robber barons were from the late 19th century. They are here now!

I have the same situation in the house that I just moved into, from half way across the country. I dropped like 10 calls this weekend, so I'm planning on calling them up (from somewhere else) and bitching at them with the aim of getting one of these for free / rebated cost.

about a year ago i bought an Nokia e71 (for the phone integrated sip client... most nokias have that now)....I call ported my number to callcentric (att defenitely didn't like this... they were complete dinks about it).. and i bought a PAYG Card from tmobile.

All being said i'm a light 'mobile' user, and my total bills are around 15 a month for both VOIP and PAYG.

At home, I get unlimited incoming and 2c per min outgoing... ontop of that i have some bas

My boss has the same issue of it not working in his house. He had called and complained several times with no resolution. Finally, he got a "Customer Service Satisfaction Survey" where he reamed ATT in every way he could. About a week later he got a letter saying he qualified for a free MicroCell.

If I were your friend, I'd go to a corporate store (not an authorized reseller), get a manager, and ask that they give him a MicroCell for free. If they don't, demand one - or the termination of his service w

AT&T's microcell uses your broadband connection to extend their coverage and has a GPS to validate that you're using it in an 'approved area'. Also, calls don't transfer in, so you'll lose calls as you approach your house. No thanks.

"AT&T 3G MicroCell acts like a mini cellular tower in your home or small business environment. It connects to AT&T's network via your existing broadband Internet service (such as U-verse, DSL or cable) and is designed to support up to four simultaneous users in a home or small business setting."

Also,

"Calls transfer out, but don't transfer in. Calls seamlessly transfer from the 3G MicroCell to the strongest available AT&T cell tower signal. However, calls connected on the cell tower do not transfer to the 3G MicroCell."

I can see why the carrier wouldn't want calls to be handed off from an official base station to a private station, especially if the end user has no choice or say so. There could be a slew of problems, anything from poor latency, low bandwidth, to potential eavesdropping or monitoring. The carrier would be blamed for the poor connection of a femtocell without the end user even knowing the logistics involved.

The fact is, if you don't have cell service at your house, then you aren't any worse off for those sp

Well, the AT&T femtocell only allows registered cellphones on it, so the issue about bad connection or eavesdropping is irrelevant. You bought it, so if your connection didn't work well with it, you probably immediately returned it. And it is your broadband service so you'd be eavesdropping on yourself. Bad connection to foreign femtocells could be an issue if AT&T allowed any cellphone to connect. But the data transferred over the broadband connection should be strongly encrypted, so eavesdropping

Well, the AT&T femtocell only allows registered cellphones on it, so the issue about bad connection or eavesdropping is irrelevant.

It only allows AT&T registered numbers on it. It doesn't care who those numbers belong to, as long as they're with AT&T.

I have two of these devices at work and after getting them registered (using a AT&T number on our corporate account) I've been able to add any AT&T number I've tried to them, ranging from other people on the corporate account to clients or guests who were just visiting the office for one day. As long as it's an AT&T number, it will work, and it will make calls using the

I figured it was like the proposed magicjack femtocell, where you have to grant permission for your phone to connect to the femtocell, so a femtocell owner couldn't add your phone as an allowed device without your knowledge. If not, eavesdropping could perhaps be a concern.

But AT&T should have really configured the femtocell to require phones connecting to it set up an encrypted wireless channel, and all the backhaul from the femtocell to the AT&T network over your broadband should also be strong

While on the landline network someone can just climb up a pole and attach a monitoring device to your phone line. Some monitoring devices don't even require direct electrical coupling to the line. If they were smart about it I doubt anyone would notice they weren't a legitimate telecom engineer.

The fact is phones whether fixed line or mobile are not secure from either the government or a sufficiently motivated private entity. If secret information is being handled they should be treated as such.

Very true. But I still think each mobile phone operator should make a best effort to secure their part of the GSM network, and that includes their carrier sold phones to require an encrypted wireless channel to the base station, and any picocells they provide to encrypt traffic over its backhaul. Doing these 2 things would make a mobile to mobile or VOIP phone call relatively secure against all but the government and really motivated private parties.

The biggest problem with femtocells is that customers expect them to be free. This isn't unreasonable, after all they're paying a monthly fee to get a service and they expect that they can stand in the bathroom in their city centre flat and be able to make a call.

The problem is that building a business case for purchasing a tonne of femtocells and giving them away to customers for nothing isn't a pretty read and getting a director to sign off on such an endeavour has been tough.

They'd far rather that the money was spent solving the signal problems (which improves things for everyone, not just the femtocell owner - but at the cost of a slow resolution time) rather than publicly admit that their signal is rubbish in urban places and needs "boosting".

The biggest problem with femtocells is that customers expect them to be free. This isn't unreasonable, after all they're paying a monthly fee to get a service and they expect that they can stand in the bathroom in their city centre flat and be able to make a call.

It isn't so much that they aren't free... It's that they cost so much, while costing me additional resources, and not really doing much for me except allowing me to use the device that I'm supposed to be able to use anyway.

I have a Verizon cell phone. According to all their coverage maps, I should be fine. I'm not. I routinely drop calls at home. Regardless of what they say, we're right on the edge of their coverage.

Verizon offers a femtocell for $250. This femtocell will use my electricity, it will use my bandwidth, and it will not save me any money at all. I still get charged for calls and data at the normal rate even though I'm having less of an impact on their infrastructure. All I get for my money is the ability to use my cell phone in an area where they swear I should be able to use it anyway.

I wouldn't complain if the femtocell was just $50... Or if they took $5/month off my bill... Or if calls/data/whatever were discounted while using the femtocell...

I wouldn't complain if the femtocell was just $50... Or if they took $5/month off my bill... Or if calls/data/whatever were discounted while using the femtocell...

I had Sprint's airave box for a while. It made for good coverage (there was a hill between the closest sprint tower and my house), but the fact that I paid extra per month just so I could have the box irked me. Then I elected to pay even more per month for the "completely unlimited airtime" option when placing calls through the airave box.

That depends, of course, on who is deploying them. An existing ISP, for example, could deploy a cellular network pretty much instantly by providing the femtocells to their customers and buying capacity on an existing network.

A good candidate for doing that here in the UK would be Virgin Mobile, a virtual operator owned by Virgin Media, the largest ISP in the UK. If Virgin Media provided cable modems with built-in femtocells, they'd reduce their operating costs, because most calls in urban areas would be

That's a rather good idea, I like it. Would also work for companies like O2 and Orange who also provide broadband.

Unfortunately it's been a while since I received quotes from femtocell manufacturers and back then they weren't cheap. Plus the people making the routers didn't have the experience to build such capability in.

If AT&T can provide them for $99, they can't cost much more than that wholesale. A few companies offer femtocell SoCs, so router manufacturers can just connect them up to power, an antenna, and Ethernet, in the same way that they do with 802.11 chips. Given the quantity of that a company like VM buys, I think they could probably say 'we want a small box that does 802.11n, Ethernet, DOCSIS3, HSPA and GSM' and have several companies offering to produce them.

It's not even that the hardware isn't free (like it should be), but when you're using it you're using up your own power and bandwidth (after you already shelled out $100 for the hardware), and the companies still charge your minutes when you're using it.

Why should I pay money for a device which uses my power and my DSL connection to relay my calls, and then let the cellular carrier charge me for the "airtime"? Especially since there are WiFi alternatives?

That's not what this article is talking about. The cell phone carriers are just putting small mini-towers on lots of telephone poles instead of putting in massive towers. Less regulatory hassle, less NIMBY, and more targeted coverage.

It's not just a "Can I build it?" problem. In the US, you have to be properly licensed to transmit. The micro/femtocells the carriers are releasing are covered under their FCC license & authorization. If you built an OpenBTS box and wanted to use it at home, you'd have to obtain an FCC license for the transmitter. You'd also have to coordinate frequency plans with the other carriers operating in your area.

Read about the fun the guys at Burning Man went through to set theirs up.

Not if you care about little things like legality. Using OpenBTS requires a license for the spectrum. Network operators and anyone who bought a license for the relevant spectrum can deploy OpenBTS. Individuals can not (unless they get an exemption for a test network, as Burning Man did, or unless they are in some unregulated area, like the middle of the ocean).

I've noticed that there seems to be sufficiant overlap between the E-GSM-900 band and the 902–928 MHz ISM band in the US that you should be able to get some uplink and some downlink channels within the ISM band.

Anyone have any thoughts on the legality of doing this if the power was kept low enough?

The way I look at it, if cell service isn't provided to your area or it's that crappy, either get a different provider or don't give them any money at all. Get Skype or some other VoIP provider (or now use Google VoIP unlimited for free) and then lower your cell to its lowest number of minutes. The difference between basic minutes and unlimited is like $30/mo. And a femtocell is just VoIP.

Why pay $100 on top of your monthly bill to get service, when you can just not pay extra and actually pay less?

If such a device is available it will only be a matter of time before someone makes a network using only these type of devices and perhaps slightly more powerful ones with an outdoor antenna. Its already possible to set up your own GSM network using a USRP and route the calls over SIP.

Give it a few more years and they will have femtocells for 4G. The only 'mobile operator' that will be necessary is some guy with a server to do the accounting (which femtocell gets the most traffic and allocate credits fro